Shuttle-type transportation or conveying systems have been employed in which two passenger or load carrier units are coupled in a loop-type haul rope and driven back and forth between terminals, usually located proximate the ends of the haul rope loop. Such systems may or may not include intermediate terminals, and the passenger carrier units may be supported by wheels on a support surface or track, or suspended from the haul rope by means of support sheaves over part or all of the path.
A constant problem in such shuttle tramway systems is maintaining uniform, and preferably symmetrical tensioning forces in the haul rope. This is usually accomplished at the haul rope drive or bull wheels or through a counterweight assembly acting on the haul rope. Counterweight systems result in rope tension forces which are not always symmetrical in terms of the direction of driving of the haul rope, and bull wheel tensioning systems require complex carriage mounting assemblies.
Another difficult problem in connection with shuttle tramway systems is the problem of accurate docking at the terminals. Federal handicap access regulations require, for example, that there be no more than a one inch gap between the passenger carrier unit and the terminal at the ingress and egress doors.
In haul rope-driven conveying systems, the bull wheel which drives the haul rope can only be slowed and stopped with a certain degree of precision. It is desirable to accelerate the carrier units from zero to their maximum velocity and then decelerate them back down to zero at rates which are comfortable to passengers. The mass of the carrier units and their load will, however, cause elastic stretching and even oscillation of the haul rope during the docking process, and can produce slippage of the haul rope with respect to the driving bull wheel. Thus, over time, the combination of bull wheel imprecision, haul rope elasticity and carrier unit mass will create unacceptable docking imprecision, which in turn requires system adjustments. The problem is further complicated when two passenger carrier units are driven by a single haul rope in a shuttle system at which the passenger carrier units must dock simultaneously at opposed end terminals.
In various urban environments, for example, at airports, considerable use of shuttle conveying systems has been made. Most of these systems, however, tend to be based upon a single car or passenger carrier unit that is rail-mounted driven by a motor carried by the car or by driven tires adjacent to the car along the path to be travelled. Very little has been done with haul rope-driven passenger conveying systems in urban applications.
Accordingly, it is an object of the present invention to provide a tensioning apparatus and method for a haul rope-driven transportation system which allows symmetrical rope tension to be achieved regardless of the direction of haul rope advancement.
It is another object of the present invention to provide a haul rope-driven, load carrying, conveying or transportation system having a docking assembly which is capable of precise, repeated docking of the load carrying units or vehicles at terminals.
Another object of the present invention is to provide a load carrying conveying system and method in which the load carrying units can be displaced on the driving haul rope to ensure proper docking of the units at terminals for loading and unloading of passengers and other loads.
Still another object of the present invention is to provide a haul rope-driven passenger conveying system suitable for use in urban environments and having improved tensioning and docking capability.
Still a further object of the present invention is to provide a shuttle-type passenger conveying system which is durable, has a minimum number of components, can be easily repaired and maintained, and does not require an on-board operator.
The conveying system of the present invention and method have other features and advantages which will become apparent from and are set forth in more detail in the following description of the Best Mode Of Carrying Out The Invention.